This invention relates to prosthetic devices and in particular to a foot prosthesis for amputees. The lower extremity of prosthetic devices for both below-knee and above-knee amputees is conventionally rigid with minor added cushioning particularly at the heel to allow the amputee a relatively firm control over the foot while walking.
Because the dynamic forces on the prosthetic leg and foot device are severe, the sculptured foot member is securely fixed to the leg member to form a rigid integral structure. Customarily, the amputee participates in the alignment and adjustment of the foot block prior to final shaping and bonding to the leg or ankle block. The resulting structure integrated leg is a laminated member that is permanently fixed to prevent subsequent misalignment. The initial alignment and adjustment fixes the heel height to a particular shoe and the user must continue to wear shoes that have identical heel heights. This often requires the amputee to wear the same model shoe, always. If a different shoe is worn, the stability of the prosthesis is affected, resulting in unnatural gait, and in some cases, an unsafe limb. While the leg member can be subsequently severed, realigned and adjusted for a different heel height, and again laminated, the user is again limited to a fixed prosthetic member.
The advantage of a prosthetic leg having a foot member with an adjustable heel height can be readily appreciated. The user can manually adjust the heel height of the foot member to the optimum position for comfort and safety for the particular shoes that he is wearing. This adjustment capability allows the amputee, with minor training, to self-adjust for any heel height he chooses. He is then afforded a wide variety of shoes, from heelless slippers to high heel boots.
A principal obstacle to a leg prosthesis with an adjustable heel is the tremendous dynamic forces applied to the prosthetic structure during even the simple act of walking. Further, because no wobble or misalignment can be tolerated, for obvious reasons of balance and safety, an adjustment mechanism must be strong and free from any problems of wear or loosening that would affect stability. Yet, the mechanism must be sufficiently compact to be concealed within the leg member. The adjustable prosthetic ankle assembly of this invention solves these problems and incorporates a safe adjustment mechanism into a leg prosthesis. The invented adjustable prosthetic ankle assembly provides a reliable and comfortable alternative to the fixed structure of the conventional device.